There’s a Fix for that

I posted the video yesterday, but didn’t have time to write the post to go with it due to having to go out while it was still uploading. Anyway, here’s the update.

Following on from Knuckle Bash, Dogyuun and V-Five, Robiza managed to decrypt the Sound CPU code for FixEight, which uses a different encryption table.

Previously only a bootleg was ‘working’ and that had vastly inferior sound hardware. (and a much lower CPU clock resulting in large slowdowns.)

Unlike Toaplan’s other games FixEight uses an EEPROM for settings / region selection, which caused a few additional issues. I’ve helped Robiza with most of these, and the game correctly loads and saves it’s settings from EEPROM. The only thing strange is that the EEPROM that was dumped from the original PCB appears to be non-functional with the code we have; there are explicit checks for values stored in it, and they’re simply wrong in the dump. Also due to Toaplan using a non-user-changable EEPROM setting for the region in this we have to support the regions as a bunch of clones rather than having the jumper switch if we’re to avoid using hacks in the code.

The Sound CPU in this instance also provides background data (they’re contained scrambled in the program ROM, the V25 program descrambles them) We knew that the sound CPU was involved with the backgrounds somehow, but weren’t sure exactly. It turns out they use an almost identical method to the one used to load the 2nd part of the v25 code on the other games, copying the background data once at startup into shared RAM. Note, even the bootleggers resorted to placing this data in an additional ROM because they couldn’t figure out how the V25 descrambled the data from ROM.

I don’t think this is one of Toaplan’s better games. It’s meant as a followup to the excellent OutZone but the environments are too claustrophobic, and don’t give you enough room to shoot. Coupled with some rather useless alternate weapons which just end up in a single direction, or simply hitting the level environment instead of your enemies and you have what can only be described as a frustrating experience. A Shame, because it’s a very good looking game. The music isn’t even that good, although is infinitely better than that found in the bootleg!

Note, the intro ONLY plays if the invincibility setting is set to ON. I don’t know if this is because Toaplan decided to take the feature out of the game, or if there is another revision with this condition / bug fixed. The bootleg in MAME is the same. There is an explicit check in the code and the bit to enable the intro is exactly the same as the bit to enable invincibility! This seems illogical, but it’s the way it is.

The remaining Toaplan games (Vimana, FireShark, Ghox, Whoopee JPN version, Teki Paki) will need the HD647180 MCUs decapping for proper sound emulation.
See The Decapping project for more information on this. Donations _are_ required if this work is to be done. Proper emulated sound will be far better than the hacked in OSTs found in some other builds as has been shown with the ones we’ve emulated here. As a programmer there is nothing more I can do for those games, in order to emulate the sound, we need the sound code, which is inside the MCU.

Chips 19, 58, and 102 are the Toaplan MCUs. Please note, he does not yet have the MCU for Ghox, or the Japan Whoopee (although the latter I believe has been sourced) Spares of the chips always help in the case of something going wrong.







Source: mamedev.emulab.it/haze/